Controlled atmosphere gravity casting system

ABSTRACT

An improved system for evaluation of unique materials formed by quenching the same in their liquid state under predetermined controlled uncontaminated gaseous environment. The apparatus permits rapid solidification of the material in the desired gaseous atmosphere such that the possibility of undesirable oxidation or contamination is minimized.

[451 June 6,1972

United States Patent Thomas, Jr. et al.

.164/258 X Hitchings...........................164/136 X A n m .w m tr.hk mm NN TS 7900 555667 999999 wmwmww 09968 97565 483229 680355 .7999222223 N m w. m 3 m .m 1m H mm M J m m an 3 PS mm m G m MN K w I, t A mm DS m U 3 1 m .m WH MT T T: m mum C G .m A M .4 M U U U represented bythe Secretary of the Navy Primary Examiner R Spencer Annear [22] Filed:Oct. 22, 1970 Attorney-Richard J. Miller and R. S. Sciascia [21] Appl.No.:

[57] ABSTRACT An improved system for evaluation of unique materialsformed by quenching the same in their liquid state under [52]U.S.CL................. .......164/258,164/136, 164/259,

164/336 27/16 164/61, 65, 66, 68, 136, 254, predetermined controlleduncontaminated gaseous environ- 164/256, 258, 259, 335 ment. Theapparatus permits rapid solidification of the material in the desiredgaseous atmosphere such that the possibility of undesirable oxidation orcontamination is minimized.

[51] Int. [58] Field ofSearch..................

References Cited 8 Claims, 3 Drawing Figures UNITED STATES PATENTS1,897,589 Reeve...........,......................164/65 X PATENTEDJUH 6I972 SHEET 10F 2 FlG.l

MARSHALL K.THOMAS,JR. JAMES M THOMPKINS War/neg PATENTED H 6M2 3.667.535SHEET 20F 2 l/w m fags 4 I, 1

MARSHALL K. THOMAS, JR. JAMES N THOMPKINS CONTROLLED ATMOSPHERE GRAVITYCASTING SYSTEM The invention provides a method of quenching a liquidmetal from a controlled gaseous environment as rapidily as possiblewithout the contamination from ambient conditions during cooling. Bothan uncontaminated quenching environment and rapid quench are essentialsince during the time of quenching dissolved gases in the liquid metalcould be lost and gases from the atmosphere absorbed. It is alsoessential that the solid sample not have any detectable oxide or scaleon its surface.

In the State-of-the-Art samples where prepared from a crucible, whichcontain liquid metal, wherein the sample was lowered from the furnace tothe water quenching section and cooled therein. These samples had oxidesurfaces and had scaling plus additional oxidized holes. In addition theprocedure of solidification was relatively slow taking 35 to 45 secondsfrom the liquid state of copper at 1550 C to a solid state. It wasobvious that there was contamination from the atmosphere and anadditional oxide scale was produced on the surface of the sample.Removal of the sample required an additional step of grinding while initself was not perfect since small bits of oxide could be lost. Inaddition oxide layers could be generated by the heat of grinding.Further, non-uniform distribution of oxygen in the sample would causeerrors in analysis.

It is therefore an object of this invention to provide an improvedmethod of quenching a liquid metal specimen in a controlled atmosphereenvironment.

It is a further object of this invention to provide an improved liquidsample quenching system wherein the liquid metal is poured into a moldfor producing castings of predetermined configuration.

Yet another object of this invention is to provide an improvedcontrolled atmosphere liquid metal quenching system, comprising: acontainer for holding a metal to be heated to the liquid state; meansfor heating the container and metal to the melting point of the metal;support means for maintaining the container in the heating means and forcausing the metal when heated to the liquid state to leave the containerunder the influence of gravity; a cooling chamber for receiving theliquid metal; a mold coupled to the cooling chamber for receiving theliquid metal and to hold it ,while cooling to the solid state; and ameans for providing a controlled atmosphere surround the liquid metal atall times during the heating and cooling steps until it is in the solidstate and its temperature has been reduced to a point wherein rapidoxidation will not take place.

A further object of this invention is to. provide an improved controlledatmosphere liquid metal quenching system, comprising: furnace meanshaving a hollow portion; a sample holder for liquid metal positionablein the hollow portions; actuating rod support means in the furnacerotatable between two positions, the first position supportingthe sampleholder, the second position releasing the sample holder from within thefurnace; a cooling chamber coupled to the furnace and directly below thehollow position; means in the cooling chamber for mounting the samplerholder to release the liquid metal; a molding means coupled to thecooling chamber to receive the liquid metal; means for cooling thecooling chamber and the molding means to bring the liquid sample to asolid state temperature; and an atmosphere control means coupled to thefurnace, drop chamber and the mold for cleaning and purging the systemand for providing an inert atmosphere during the heating, cooling andsolidifying phases of the quenching system to prevent oxidization andimpurity inclusion.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic layout of the system;

FIG. 2 is a detailed drawing of the furnace, cooling chamber and mold;and

FIG. 3 is a further detail of that portion of the furnace containing thecrucible, and crucible support.

Referring now generally to the Figures, a furnace 10 is shown having ahollow section 11 connected to a tube 12, through a connector 13 to adrop or cooling chamber 14. A mold section 15 is provided and a set ofcooling coils l6 surrounds the cooling section-of both the mold sectionand the cooling chamber. An atmospheric control system is generallydesignated as 20 to include a series of stopcocks 21, 22, 23 and 24,interconnecting a source of vacuum 25, not shown, a vacuum gauge 26, asource of inert gas 27, a water manometer 28, and a water bubbler 29.This system is coupled through a pair of connections 30, 31 to thefurnace and the drop chamber.

FIG. 3 shows a partial cross-sectional view of the details of thatportion of the furnace wherein there is supported a crucible 40,containing a liquid metal 41 and a gas delivery tube 42. The entire unit41 supported upon an actuatable rod 44 having at least two positions,the first position being that which supports the crucible in astationary position during the heating of the metal to the liquid state.The second position of the rod 44 is a position rotated away from thesupport position so that the crucible 40 is released for free fall.

FIG. 2 shows the crucible in two stages of free fall after hav ing beenreleased by the rod 44. The first stage, the crucible has followed apath down through the upper position of the quenching or cooling chamber14 and in position shown, designated as 50, the crucible has hit thepair of copper pins 51, 52, positioned such that the center of momentabout the base of the crucible 40 is such that it rotates into theposition shown as 55. It should be noted that in any given moldingoperation there is only one crucible within the quenching chamber, butfor the sake of clarity, two are showninto successive positions 50 and55. The liquid metal 41 is shown descending into the inner portion 58 ofthe mold. In one embodiment of the invention where specimens are beingprepared for further gas analysis the exact shape of the specimen is notcritical, however, it should be noted that if a casting operation is tobe performed the mold portion 58 would have a specific configurationsuch as to provide the desired casting. After a predetermined coolingperiod mold 15 is removed and the specimen removed from portion 58.

The general operation of the apparatus is as follows. Initially all ofthe stopcocks 21, 22, 23 and 24, and the vacuum type ball 59, in FIG. 3,are in the closed position. The system is evacuated by opening stopcock21, which is connected to the vacuum system 25, and two way stopcock 23is positioned so that it is open to the vacuum line. Pressure ismonitored with the vacuum gauge 26 and in one instance when the vacuumreached 200 microns or less the stopcock-23 is open to admit argon gaswhich has been purified by passing over fine copper tumings at 600 C andthe vacuum line is blocked off from the quenching chamber. Time isallowed to elapse to further purify and purge the system, the platinumrod is positioned in its support position with a crucible having a metalsample to be melted and the quenching chamber is attached, as shown inFIG. 1. Stopcock 22 is opened and adjusted to provide a slight pressureof 0.5 centimeters of water at the bottom furnace 12. This procedureflushes any residual air in the bottom of the furnace. Valve 23 isopened to relieve the high pressure of the argon gas in the quenchingchamber through bubbler 29. The ball valve 59 is slowly opened whilestopcock 22 is manipulated to maintain a slight positive pressure.

When the ball valve is completely opened the crucible 40 is dropped byrotating the platinum 44 from its first to its second position. Thecrucible'is dropped and a temperature change at the water cooled moldindicates that in fact the crucible has tipped.

After the sample has been dropped, ball valve 59 is rotated to theclosed position, valve 22 is closed, the clamps 13 are released and thequenching chamber is removed from under the furnace allowing the nextsucceeding sample to be inserted into the bottom of the furnace.

The quenching chamber is allowed to stand for a period of time, in onesuccessful embodiment of the invention 15 minutes, to make certain thatthe sample has reached room temperature and that there is no chance ofoxidation.

The removal of the sample is accomplished by closing stopcock 23,cutting off the flow or argon, in thiscase the inert atmosphere. Thecooling water to the quenching chamber is turned ofi permitting thecopper mold to warm up to room temperature before it is sealed toquenching chamber for the next run. One additional advantageof this isthat the sealing compound, coupling the furnace to the quenching chamberseals better if the temperature is 25 C or higher. The quenching chamberis then inverted and the sample removed.

If it were desirable to cool the liquid sample even more rapidily itshould be noted that instead of cooling water circulating about thequenching chamber it would be possible to design the system to provideliquid nitrogen or some other coolant as the temperature controller ofthe mold. Further the entire quenching chamber could be immersed in acontainer to provide more efficient cooling of the chamber.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings it is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

We claim:

1. An improved controlled atmosphere liquid metal quenching system,comprising:

a. a container for holding a metal to be heated to said liquid statecapable of free fall:

b. means for heating said container and metal to the melting point ofsaid metal:

c. support means having first and second positions, said first positionsupporting said container in an upright position and said secondposition causing said container to free fall for maintaining saidcontainer in said heating means and for causing said metal when heatedto said liquid state to leave said container under the influence ofgravity;

. a cooling chamber for receiving said liquid metal;

e. a mold coupled to said cooling chamber for receiving said liquidmetal and to hold it while cooling to the solid state; and

. a means for providing a controlled atmosphere surrounding said liquidmetal at all times during the heating and cooling stages until it is inthe solid and its temperature has been reduced to a point wherein rapidoxidation will not take place.

2. The system of claim 1 wherein said container is a crucible having anopen end and the supporting means is a rod rotatable between first andsecond positions, said first position supporting said crucible in theupright position and in the second position allowing said crucible tofall.

3. The system of claim 2 wherein said cooling chamber has meanspositioned therein to rotate said crucible to a position where theliquid metal freely falls therefrom.

4. The system of claim 3 wherein a cooling jacket is provided about saidcooling chamber.

5. The system of claim 4 wherein the coolant in said cooling jacket iswater.

6. The system of claim 4 wherein there is provided a vacuum systemcoupled to said controlled atmosphere system for cleansing and purgingthe atmosphere in the heating means, the cooling chamber and the mold.

7. The system of claim 6 wherein said crucible is made of aluminium thesaid support rod of platinum.

8. An improved controlled atmosphere liquid metal quenching system,comprising:

a. furnace means having a hollow portion;

b. a sample holder for liquid metal positioned in said hollow portion;

c. actuating rod support means in said furnace rotatable between twopositions, said first position supporting said sample holder, saidsecond position releasing said sample holder from within said furnace;

d. a cooling chamber coupled to said furnace and directly below saidhollow position;

e. means in said cooling chamber for mounting said sample holder torelease said liquid metal; f. a moulding means coupled to said coolingchamber to

1. An improved controlled atmosphere liquid metal quenching system,comprising: a. a container for holding a metal to be heated to saidliquid state capable of free fall: b. means for heating said containerand metal to the melting point of said metal: c. support means havingfirst and second positions, said first position supporting saidcontainer in an upright position and said second position causing saidcontainer to free fall for maintaining said container in said heatingmeans and for causing said metal when heated to said liquid state toleave said container under the influence of gravity; d. a coolingchamber for receiving said liquid metal; e. a mold coupled to saidcooling chamber for receiving said liquid metal and to hold it whilecooling to the solid state; and f. a means for providing a controlledatmosphere surrounding said liquid metal at all times during the heatingand cooling stages until it is in the solid and its temperature has beenreduced to a point wherein rapid oxidation will not take place.
 2. Thesystem of claim 1 wherEin said container is a crucible having an openend and the supporting means is a rod rotatable between first and secondpositions, said first position supporting said crucible in the uprightposition and in the second position allowing said crucible to fall. 3.The system of claim 2 wherein said cooling chamber has means positionedtherein to rotate said crucible to a position where the liquid metalfreely falls therefrom.
 4. The system of claim 3 wherein a coolingjacket is provided about said cooling chamber.
 5. The system of claim 4wherein the coolant in said cooling jacket is water.
 6. The system ofclaim 4 wherein there is provided a vacuum system coupled to saidcontrolled atmosphere system for cleansing and purging the atmosphere inthe heating means, the cooling chamber and the mold.
 7. The system ofclaim 6 wherein said crucible is made of aluminium the said support rodof platinum.
 8. An improved controlled atmosphere liquid metal quenchingsystem, comprising: a. furnace means having a hollow portion; b. asample holder for liquid metal positioned in said hollow portion; c.actuating rod support means in said furnace rotatable between twopositions, said first position supporting said sample holder, saidsecond position releasing said sample holder from within said furnace;d. a cooling chamber coupled to said furnace and directly below saidhollow position; e. means in said cooling chamber for mounting saidsample holder to release said liquid metal; f. a moulding means coupledto said cooling chamber to receive said liquid metal; g. means forcooling said cooling chamber and said molding means to bring said liquidsample to a solid state temperature; and h. atmosphere control meanscoupled to said furnace, drop chamber and said mold for cleaning andpurging said system and for providing an inert atmosphere during theheating, cooling and solidifying phases of said quenching system toprevent oxidization and impurity inclusion.